Solution

redirect_uri. The URL that you want to redirect the person logging in back to. This URL will capture the response from the Login Dialog. If you are using this in a webview within a desktop app, this must be set to https://www.facebook.com/connect/login_success.html

If you’ve been using PhFacebook there wasn’t anything you had to do until now.

However if you have been trying with a different redirect_uri, fix this up now and keep reading.

The change (it seems) is that you are now required to explicitly set the redirect uri.